Search

Phosphazene base, P2-tBu, efficiently catalyzed the telescopic three-component reaction of diethyl phosphite, cinnamonitrile derivatives, and N-Boc imines, providing β-aminophosphonates having a tetrasubstituted carbon in a highly diastereoselective manner. The reaction involves the little-known 1,1-difunctionalization of an electron-deficient alkene, offering a new format for the three-component reaction under Brønsted base catalysis. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of two distinct novel series of compounds, [II]n and [V]n, containing 1,3,4-thiadiazole units, were studied in this work. The central core of the first series is phenyl, whereas the central core of the second series is OCH2CH2O. FTIR,1HNMR,13CNMR, and mass spectroscopy are used to characterize the materials used in this investigation. Liquid crystalline properties were confirmed by the use of differential scanning calorimeter (DSC) and hot-stage polarizing optical microscopy (POM). While other compounds showed no liquid crystalline behavior, the compounds [II]3–[II]6, [V]1and [V]n showed enantiotropic nematic and smectic phases. [ABSTRACT FROM AUTHOR]

The magnesium-mediated addition of bromoform to conjugated electron-deficient alkenes and imines, such as para -quinone methides (p -QMs) and aurone-derived azadienes, respectively, is reported here for the first time. While p -QMs undergo exclusive and hitherto unreported 1,6-addition of bromoform to afford benzylic tribromomethylated diarylmethanes, aurone-derived azadienes undergo both 1,2- and 1,4-additions to furnish α- and γ-tribromomethylamines. A mechanism involving the intermediacy of the tribromomethyl radical has been proposed based on control experiments and EPR studies. Representative synthetic transformations have also been carried out. [ABSTRACT FROM AUTHOR]

A dearomatization-guided and (3+2) cycloaddition-triggered annulation reaction of in situ formed isoquinolinium ylides with sulfamate-derived cyclic imines is reported, offering a cogent synthesis of tetracyclic 1,3-benzoxazepine frameworks in high yields. The protocol features successive ring-forming and ring-breaking events in a cascade fashion and is also scalable. [ABSTRACT FROM AUTHOR]

With recent developments, covalent organic frameworks (COFs) have attracted considerable attention in various applications, including visible light photocatalysis. Considering the properties of pyrene planum and π‐electron conjugation, 2D sp2 carbon‐conjugated and imine‐linked pyrene COFs, Py‐sp2c‐COF and Py‐COF are synthesized with a well‐ordered crystalline structure. Py‐sp2c‐COF is significantly superior to Py‐COF for selective photocatalysis due to the sp2 carbon conjugation. By virtue of the porosity and activity, Py‐sp2c‐COF with TEMPO ((2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl) turns out to be effective for selective aerobic oxidation of amines to imines induced by green light. Substantially, 2 mol% of TEMPO, an electron–proton transfer mediator, facilitates the aerobic conversions of amines by Py‐sp2c‐COF photocatalysis. It is an ingenious design for selective organic transformations by cooperative photocatalysis of an sp2 carbon‐conjugated COF with a redox mediator. [ABSTRACT FROM AUTHOR]

The activation of C−C bond of benzocyclobutenones under mild reaction conditions remains a challenge. We herein report a photoinduced catalyst-free regio-specific C1−C8 bond cleavage of benzocyclobutenones, enabling the generation of versatile ortho-quinoid ketene methides for aza-[4 + 2]-cycloaddition with imines, which offers a facile route to isoquinolinone derivatives, including seven family members of protoberberine alkaloids, gusanlung A, B, D, 8-oxotetrahydroplamatine, tetrahydrothalifendine, tetrahydropalmatine, and xylopinine. Furthermore, the catalytic enantioselective version of this strategy is also realized by merging synergistic photocatalysis and chiral Lewis acid catalysis. Mechanistic studies provide compelling evidence to rationalize the photoisomerization/cycloaddition cascade process. The activation of C-C bond of benzocyclobutenones under mild reaction conditions remains a challenge. Herein, the authors report a photoinduced catalyst-free regio-specific bond cleavage of benzocyclobutenones, enabling the generation of ortho-quinoid ketene methides for aza-[4 + 2]-cycloaddition with imines. Catalytic asymmetric version is also realized with Ni catalysis. [ABSTRACT FROM AUTHOR]

We report here the use of amidophosphine borane {(BH₃)₂(PPh)₂N(CH₂)C₆H₅} as a competent reducing agent for the hydroboration of ketones and imines under mild and catalyst‐free reaction conditions yielding the corresponding secondary alcohols and secondary amines after aqueous work. Solid amidophosphine boranes, which are easy to synthesize, and easy to handle demonstrated excellent reactivity and functional group tolerance toward a wide variety of ketones and imines, including aromatic, heteroaromatic, and aliphatic derivatives with electron‐withdrawing and electron‐donating substitutions, thus showing excellent chemoselectivity. [ABSTRACT FROM AUTHOR]

A strategic approach to incorporate CF3 group into oxindoles, pyrrolidines, and isoxazolones to construct spiro heterocyclic skeletons with quaternary carbon stereocenters was developed. Using a DMAP catalyst under mild conditions, the controllable synthesis of spiro oxindole‐pyrrolidine‐isoxazoline derivatives was achieved via concerted 1,3‐dipolar cycloaddition reactions of arylidene isoxazolones with N‐(2,2,2‐trifluoroethyl)isatin ketimines. This method exhibits robust regioselectivity and provides a series of isoxazolone‐based bispiro heterocycles in good to high yields (72 %–99 %) with excellent diastereoselectivity (in all cases >20 : 1 dr), offering new candidate compounds for drug screen. [ABSTRACT FROM AUTHOR]

Herein, we focus on the kinetico‐mechanistic studies of a carboxylate and Cu(II)‐assisted synthesis of imidazo[1,5‐a]pyridines encompassing C(sp3)−H amination and cyclization of imines coupled with C(sp2)−H cyanation using time‐resolved UV‐Vis reaction monitoring and ex‐situ analyses. Thus, kinetic studies have been carried out, providing a proof of the elementary steps involved, allowing for batch analysis of the compounds present in solution via MS. The experimental data obtained are consistent with the formation of a cyclometalated complex (k1) involving a C(sp3)−H bond cleavage followed by a reductive elimination/proton abstraction event (k2), both showing high enthalpy‐demanding transition states. The two processes show a well‐defined Eyring behavior with values of ΔH≠ and ΔS≠ within the expected range. Further insights on the intermediate fast C(sp2)–cyanation are also presented together with control reactions. [ABSTRACT FROM AUTHOR]

The catalytic asymmetric allylation reaction involving allylboron species has emerged as a powerful tool to access highly stereoselective allylation products. In the early years, most of the researches focused on the reaction of unsubstituted allylboronates with ketones or imines. With the synthesis of complex substituted allylboronates, allylboronic acids and allyltrifluoroborates, the type of reactions and the variety of substrates are greatly expanded. Therefore, this review article will emphasize on the aspect of regio‐ and stereoselectivity when substituted allylboron species involving and their application on the construction of versatile organic building blocks, drugs and natural products. [ABSTRACT FROM AUTHOR]

Ag‐catalyzed enantioselective 1,3‐dipolar cycloaddition of N‐2,2,2‐trifluoroethylisatin ketimines with conjugated exocyclic double bonds including α‐alkylidene succinimides and aurone derivatives was developed for the first time. Using a catalyst system consisting of a ferrocenyl P,N‐ligand and AgNO2, the reaction provides a facile method for the construction of chiral pyrrolidines bearing four consecutive stereocenters and two adjacent spiro‐quaternary chiral centers, as well as offers a direct route to structurally diverse enantioenriched CF3‐containing 3,2′‐pyrrolidinyl spirooxindole derivatives. [ABSTRACT FROM AUTHOR]

Azomethines is a class of compounds, which have traditionally served as electrophilic substrates, but their reactions with radicals have long been limited. Photocatalysis provided ample opportunities for promoting these reactions, with wide variety of reagents serving as precursors of radicals. Besides regular addition mode at the azomethine fragment, the oxidative pathway, in which the C=N bond remains in the product, has become possible by proper selection of redox catalyst. This review summarizes new developments in this rapidly developing field over the past five years. New concepts on activation of the C=N bond towards radical attack are discussed. [ABSTRACT FROM AUTHOR]

The development of new catalytic systems that enable regio- and chemoselective construction of diversely functionalized oxazocines is an important topic in organic synthesis and pharmacochemistry. Herein, a novel Pd/Mengphos complex was designed and applied in a palladium-catalyzed high-order [4+4] cycloaddition of 2-substituted allylic carbonates to α,β-unsaturated imines, allowing facile access to versatile oxazocines in good yields with excellent b / l and Z / E selectivities (up to 92% yield and complete b / l and Z / E selectivities). The reaction exhibited a broad substrate scope, mild reaction conditions, and good functional group compatibility. In addition, an asymmetric version has also been tested, affording the desired oxazocines in moderate to good enantioselectivity. [ABSTRACT FROM AUTHOR]

The asymmetric construction of a quaternary fluorine‐containing stereogenic carboncenter is highly valuable for the development of fluoroine‐containing bioactive molecules. Herein, a base‐promoted, diastereoselective Mannich‐type reaction of 2‐aryloxy‐2‐fluoroketones with N‐(tert‐butylsulfinyl)imines has been developed. A number of the addition products featuring a fluorinated quaternary stereocarbon centre and a β‐fluoroamine structural motif have been readily obtained in good yields with moderate to good diastereoselectivities. The absolute configuration of the major diasteromer was determined by X‐ray crystallography analysis, and a closed transition‐state mode was proposed to explain the stereochemical outcome of this reaction. In addition, the addition product was efficiently converted into a α‑fluoro‐β‐amino alcohol through desulfinylation followed by reduction of the carbonyl group. [ABSTRACT FROM AUTHOR]

A Pd‐catalyzed umpolung allylation of isatin‐derived azomethine imines with vinyl cyclopropanes was disclosed. This protocol provides an efficient and atom‐economic approach to access an array of structurally interesting allylic aminooxindole derivatives in good yields and linear‐selectivities (up to 95 % yield). Further product derivatization and asymmetric catalytic studies proved the practicability of reaction and potential application. [ABSTRACT FROM AUTHOR]

The coupling between bis(2-oxazolines) and two equivalents of aromatic aldehydes in the presence of catalytic amounts of NiCl2 affords an ester-imine product in synthetically useful yields. This virtually unknown, 100% atom-economic transformation involves the formal metathesis between the C=N double bond of the bis(2-oxazoline) moiety, which undergoes ring-opening, and the C=O double bond of the aldehyde. The scope of this transformation is studied, and a mechanism is proposed based on DFT calculations. [ABSTRACT FROM AUTHOR]

Photocatalytic sulfonylation/trifluoromethylation‐peroxidation of alkenes with N‐sulfonyl ketimines and tert‐butyl hydroperoxide is reported. The transformation is initiated by the EnT‐driven homolytic S−N bond cleavage of N‐sulfonyl ketimines. The sulfonyl‐peroxides were obtained when alkyl sulfonyl radicals were captured by alkene via sequential C−S and C−O bond formation, while a thermodynamically favored release of SO2 from trifluoromethane sulfonyl radical generated CF3 radical and afforded the trifluoromethyl‐peroxides. [ABSTRACT FROM AUTHOR]

Comprehensive Summary 3,3‐Disubstituted oxindoles, forming the core of extensive bioactive natural products and drugs, attract tremendous efforts to develop efficient methods for their preparation. Here, a photocatalyst‐free approach for the synthesis of 3,3‐disubstituted oxindoles via a substrate‐photosensitive strategy under visible light was successfully developed. Preliminary mechanistic studies illustrated that isatin‐derived imines can be directly excited by visible light to generate strong oxidant states, facilitating subsequent single‐electron transfer (SET) processes with Hantzsch esters to afford the corresponding α‐amino radical intermediates. Thus, these α‐amino radicals promote the subsequent Giese radical addition or radical/radical cross‐coupling reactions to furnish diverse functionalized 3‐substituted 3‐aminooxindoles in high yields. [ABSTRACT FROM AUTHOR]

The cycloaddition reaction involving bicyclo[1.1.0]butanes (BCBs) offers a versatile and efficient synthetic platform for producing C(sp3)‐rich rigid bridged ring scaffolds, which act as phenyl bioisosteres. However, there is a scarcity of catalytic asymmetric cycloadditions of BCBs to fulfill the need for enantioenriched saturated bicycles in drug design and development. In this study, an efficient synthesis of valuable azabicyclo[2.1.1]hexanes (aza‐BCHs) by an enantioselective zinc‐catalyzed (3+2) cycloadditions of BCBs with imines is reported. The reaction proceeds effectively with a novel type of BCB that incorporates a 2‐acyl imidazole group and a diverse array of alkynyl‐ and aryl‐substituted imines. The target aza‐BCHs, which consist of α‐chiral amine fragments and two quaternary carbon centers, are efficiently synthesized with up to 94 % and 96.5:3.5 er under mild conditions. Experimental and computational studies reveal that the reaction follows a concerted nucleophilic ring‐opening mechanism of BCBs with imines. This mechanism is distinct from previous studies on Lewis acid‐catalyzed cycloadditions of BCBs. [ABSTRACT FROM AUTHOR]

A three‐component one‐pot synthesis of substituted azepines was realized by gold/magnesium orthogonal relay catalysis. The one‐pot synthesis involves simply mixing and heating propiolates, imines, and activated cyclopropanes to initiate a gold‐catalyzed aza‐enyne metathesis between propiolates and imines, followed by a magnesium‐catalyzed [4+3] cycloaddition reaction of the resultant 1‐azabutadienes and the cyclopropanes, yielding substituted azepines. The substituted azepines including 22 derivatives could be successfully prepared in good to excellent yield (61–95%). The reaction was also conducted on one‐gram scale. [ABSTRACT FROM AUTHOR]

Visible light-induced radical umpolung chemistry is utilized to synthesize trifluoromethylated unnatural a-amino acid and amine derivatives. This approach utilizes photoredox catalysis to perform a single-electron-transfer reduction of imines generating a N-centred radical that eventually migrates to the C-centre followed by a radical-radical cross-coupling to deliver reductive trifluoro-methylation products. [ABSTRACT FROM AUTHOR]

We report an H‐bond donor controlled diastereoselective switchable intramolecular aza‐Henry reaction of ketimines derived from α‐ketoesters and 2‐(2‐nitroethyl)anilines, allowing facile access to chiral tetrahydroquinolines bearing an aza‐quaternary carbon stereocenter, which are privileged scaffold for medicinal researches. While newly developed cinchona alkaloid derived phosphoramide‐bearing quaternary ammonium salt C2 selectively give cis‐adducts in up to 20 : 1 dr and 99 % ee, the corresponding urea‐bearing analogue C8 preferentially give trans‐adducts in up to 20 : 1 dr and 99 % ee. [ABSTRACT FROM AUTHOR]

Chiral 2‐azetines and allenes are highly valuable structural units in natural products and useful chemicals. However, enantioselective synthesis of both 2‐azetines and allenes has been extremely challenging. Herein, we present asymmetric construction of chiral 2‐azetines (70–98 % yields and up to 96 % ee) through chiral phosphine‐catalyzed [2+2] annulation of yne‐enones with sulfamate‐derived cyclic imines. These 2‐azetines were easily transformed into chiral allenes upon treatment with Et3SiH, BF3 ⋅ Et2O and water at rt for 2 minutes. Based on the above transformations, a concise one‐pot synthetic procedure combining [2+2] annulation of yne‐enones and sulfamate‐derived cyclic imines under phosphine catalysis and sequential reduction/isomerization/ring‐opening reaction through Et3SiH, BF3 ⋅ Et2O and water was thus set up, providing axially chiral tetrasubstituted allenes in satisfactory yields and enantioselectivities (56–90 % yields and up to 91 % ee). [ABSTRACT FROM AUTHOR]

The β‐lactam scaffolds are the prevalent structural units in antibiotics and natural products. Herein, three‐component asymmetric Kinugasa/aldol and Kinugasa/Mannich cascade reactions have been developed for constructing α‐quaternary chiral β‐lactams. This method involved the tandem reaction of alkynes, nitrones and aldehydes (or imines), resulting in the formation of three sequential stereocenters controlled by copper(I) catalysts and chiral bis(oxazolidine) ligands. The developed protocol features high enantioselectivity, good reaction efficiency, and mild operational conditions, representing a practical and sustainable synthetic tool for the construction of functionalized chiral β‐lactams. [ABSTRACT FROM AUTHOR]

Herein, the Cu‐UiO‐66 catalyst was developed for acceptorless dehydrogenative coupling (ADC) between alcohols and amines to produce imines. The Cu‐UiO‐66 catalyst was synthesized by installing Cu2+ onto Zr‐oxo clusters in UiO‐66, and the catalyst efficiently catalyzes the ADC reaction under mild and environmentally friendly conditions with excellent selectivity. Mechanistic studies reveal that the O2⋅− radicals and porosity of formed in Cu‐UiO‐66 participate cooperatively during the catalytic cycle. Meanwhile, the only by‐product of the system is environmentally benign water. Cycling tests and hot filtration tests showed that the Cu‐UiO‐66 catalyst exhibited excellent stability and catalytic activity during the reaction. Importantly, the Cu‐UiO‐66 catalyst might provide a promising strategy for the ADC reaction between alcohols and amines to produce imines. [ABSTRACT FROM AUTHOR]

Nanoparticles made of porous coordination polymers, known as metal‐organic frameworks (MOFs), are becoming increasingly popular in nanomaterials research, especially in catalytic applications. With their intricate architectures, MOFs make it possible to incorporate metal nodes, encapsulate substrates, and use functional linkers, all of which contribute to synergistic engineering. A Ni‐based metal‐organic framework sample was prepared by the solvothermal method with NiCl2.6H2O as a precursor of Ni metal and terephthalic (H2BDC) acid as a linker. The as‐synthesized NiBDC was verified by X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDX), transmission electron microscopy (TEM), and N2 adsorption/desorption isotherms. Based on these findings, we applied the as‐synthesized NiBDC to the oxidative coupling reaction of benzylamine. The results revealed that with NiBDC as a heterogeneous catalyst, the oxidative coupling reaction of benzylamine achieved a performance of 92%. Furthermore, the catalyst maintains good stability after four catalytic cycles, with an efficiency of approximately 82%. [ABSTRACT FROM AUTHOR]

An efficient enantioselective synthesis of tetrahydro‐β‐carbolines (THBCs) using chiral metal‐monothiosquaramides (M–MTSQs) was planned. The in situ generated Pd/Fe‐monothiosquaramides (Pd/Fe‐MTSQs) catalysed imine reduction of dihydro‐β‐carbolines exceptionally to afford chiral THBCs with an excellent enantiomeric excess (up to 98% ee). In a catalysis study, Pd‐MTSQ 12 a (10 mol%) was found to be more efficient than Pd‐MTSQ 12 b and Fe‐MTSQs (13 a and 13 b) for enantioselective imine reduction of DHBCs 14 a–e. All the major chiral alkyl‐THBC isomers 15 a–c (90% ee, 98% ee and 95% ee, respectively) were observed with R configuration which was explained by Si face hydride attack on alkyl DHBC imines (14 a–c). Surprisingly, S configuration was perceived for the major isomers of chiral aryl‐THBCs 15 d and 15 e (95% ee and 96% ee, respectively) which was rationalized by Re face hydride attack on aryl DHBC imines (14 d and 14 e). [ABSTRACT FROM AUTHOR]

[Display omitted] Covalent organic frameworks (COFs) have attracted significant interest due to diverse applications, relying on their versatile molecular building blocks like fluorenes. However, the twisted structures of fluorenes pose substantial challenges for the construction of porous crystalline materials like COFs. Here, the couplings of 1,3,5-triformylphloroglucinol (Tp) with 9H-fluorene-2,7-diamine (DAF), 9,9-dimethyl-9H-fluorene-2,7-diamine (MFC) and 9,9-difluoro-9H-fluorene-2,7-diamine (FFC) with a pyrrolidine catalyst afford three fluorene-based COFs, TpDAF-COF, TpMFC-COF and TpFFC-COF, respectively. The resulting COFs, with distinct functional groups, exhibit high crystallinity and porosity. Optoelectronic tests reveal that TpFFC-COF demonstrates the most intense photocurrent density and the lowest interfacial charge transfer resistance. When applied to the selective aerobic oxidation of amines to imines, the efficiency follows the order of TpFFC-COF > TpMFC-COF > TpDAF-COF, consistent with the observed optoelectronic properties. Additionally, the TpFFC-COF photocatalyst showcases excellent reusability and broad applicability. This work illuminates the potential of engineering COFs with functional groups toward efficient photocatalysts. [ABSTRACT FROM AUTHOR]

An organocatalytic enantioselective [3+2] cycloaddition reaction involving 2-arylidene-1,3-indandiones and N-2,2-difluoroethylbenzothiophenone imines was developed. This approach efficiently afforded dispiro[benzothiophenone-indandione-pyrrolidine]s, featuring three stereocenters, in 84–98% yields with 3–93% ee and 9:1–>20:1 dr. Notably, the method maintained its yield and enantioselectivity integrity even in a gram-scale amplification experiment. For example, the product with substituents on aromatics were obtained in 90% yield with 91% ee and >20:1 dr. Its absolute configuration was established through X-ray single-crystal diffraction analysis, and a plausible reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

Herein, we report an example of a stereoselective γ-addition reaction of trifluoromethyl ketimines to 1-alkynyl ketones mediated by an isothiourea, BTM, under mild conditions, which afforded tetrasubstituted allenes with central chiralities in high yields (up to 94% yield), good enantioselectivities (up to 91% ee), and excellent diastereoselectivities (all >20 : 1 dr). In addition, the BTM-catalyzed γ-addition reaction was successfully applied to the gram-scale reaction, and an unexpected benzopyrrolothiazine derivative was successfully converted, albeit racemic. [ABSTRACT FROM AUTHOR]

Chiral N‐heterocyclic compounds are key structures in natural compounds and pharmaceuticals, and they serve as essential building blocks of functional materials. Catalytic asymmetric cycloaddition reactions represent one of the most efficient synthetic strategies for constructing optically active heterocycles. Cyclic sulfamidate imines have recently come to be extensively studied and widely utilized in both organocatalytic and transition metal‐catalyzed asymmetric cycloadditions, where they have been shown to provide various N‐fused‐heterocycles and spiro‐cycles exhibiting high efficiencies with excellent stereoselectivities. This review highlights recent advancements in catalytic asymmetric cycloadditions of cyclic sulfamidate imines for the stereoselective synthesis of biologically active sulfamidate‐containing heterocycles since 2012 while focusing on the diverse reactivities of cyclic sulfamidate imines and the mechanisms of chiral induction in catalysis. [ABSTRACT FROM AUTHOR]

We demonstrate that 2‐alkenylarylaldimines and ketimines undergo thermal 6π‐azaelectrocyclization to generate a wide range of azabicyclic o‐quinodimethanes (o‐QDMs). These o‐QDMs exist as a hybrid of a diene and a benzylic diradical. The diradical nature was confirmed by their ability to undergo dimerization and react with H‐atom donor, 2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) and O2. In addition, the interception of the diradicaloid o‐QDMs by H‐atom transfer was used to synthesize five tetrahydroisoquinoline alkaloids and related bioactive molecules. The diene form can undergo [4+2] cycloaddition reactions with different dienophiles to generate bridged azabicycles in high endo:exo selectivity. The azabicyclic o‐QDMs can be generated for [4+2] cycloaddition from a wide range of electronically and sterically varied 2‐alkenylarylimines, including mono, di, tri and tetrasubstituted alkenes, and imines derived from arylamine, alkylamine (1°, 2°, 3°), benzylamine, benzylsulfonamide and Boc‐amine. [ABSTRACT FROM AUTHOR]

A series of novel bis-spiro-β-lactams were obtained by the Staudinger synthesis. Pyrazine-2,3-dicarboxylic acid was cyclized with thiosemicarbazide to yield bis-2-amino-1,3,4-thiadiazole derivative which was further condensed with some commercial quinolinone derivatives to give imines. The reaction of these new imines with phenoxyacetyl chloride in the presence of triethylamine afforded spiro-β-lactams. The structures of the synthesized compounds were deduced from their FTIR, 1H NMR, and 13C NMR spectra, and elemental analyses. [ABSTRACT FROM AUTHOR]

The catalytic activity of a Ru complex 1, bearing a fused π‐conjugated imidazo[1,2–a][1,8]naphthyridine‐based mesoionic carbene (MIC) ligand, is examined for the oxidation of primary amines. Complex 1 affords nitrile or imine depending on the nature of the terminal oxidants and solvents used in the reactions. Primary amines are converted to nitriles using NaIO4 in EtOAc/H2O mixture, whereas imines are obtained under O2 balloon pressure in toluene. A variety of nitriles and imines are accessed with high yields and selectivity. A set of control experiments, reaction profiles, and kinetic studies are undertaken to disclose the mechanistic details for nitrile and imine formation. The catalytic reactions illustrate a subtle dependency on the choice of oxidants and solvents in the oxidation of primary amines. [ABSTRACT FROM AUTHOR]

Photoswitchable imines demonstrate light‐dependent dynamic covalent chemistry and can function as molecular ratchets. However, the design of aryliminopyrazoles (AIPs) has been limited to N‐pyrazole derivatives with ortho‐pyrrolidine motifs. The impact of other functionalization patterns on the photoswitching properties remains unknown. Here, we present a systematic structure‐property analysis and study how the photoswitching properties can be tuned through ortho‐ and para‐functionalization of the phenyl ring in N‐pyrazole and N‐phenyl AIPs. This study establishes the first set of design rules for these AIP photoswitches and reports the most stable Z‐isomer of an AIP to date, enabling its crystallization and resulting in the first reported crystal structure of a metastable Z‐aldimine. Finally, we demonstrate that the AIPs are promising candidates for photoswitching in the condensed phase. [ABSTRACT FROM AUTHOR]

Pd-catalyzed sequential intramolecular annulation/intermolecular [3+2] cycloaddition of 5-allenyloxazolidine-2,4-diones with dipoles was achieved. Under palladium catalysis, various 5-allenyloxazolidine-2,4-diones reacted with 1,3-dipoles such as nitrile N-oxides, azomethine imines or nitrilimines to give a series of functionalized spiroheterocycles in high yields. The scale-up reaction and further derivation of products were successful. A plausible mechanism was also proposed based on the control experiments. [ABSTRACT FROM AUTHOR]

Herein we demonstrate an "in‐ring establishing" strategy for assembling interlocked molecules through dynamic imine formation, "establishing" the host recognition sites in situ. Using Zn2+ ions to template the assembly of a pyridine‐containing macrocycle with semidumbbell‐shaped triazole‐containing aldehyde and amine derivatives, we obtained the corresponding [2]rotaxane in high yield (85 %) after subsequent imine reduction (NaBH4) and amine protonation (NH4PF6). We performed the same three steps (assembly, reduction, protonation) to prepare a stable and highly symmetrical [5]molecular necklace ([5]MN) from 12 components (two almost‐90°‐oriented dialdehydes, two almost‐90°‐oriented diamines, four macrocycles, four Zn2+ ions) in an overall yield of 69 %. [ABSTRACT FROM AUTHOR]

Adducts of sterically hindered tellurium catecholate Te(Cat36)2 (Cat36 = 3,6-di-tert-butyl-catecholate) with diimine ligands were isolated and characterized by means of single crystal X-ray diffraction along with IR, UV-vis-NIR and NMR (1H, 125Te) spectroscopy. Adducts with 1,10-phenanthroline (phen) and 5,6-epoxy-5,6-dihydro-[1,10]phenanthroline (phenO) feature a very rare μ-κ2N,N′:κ2N,N′-bridging coordination mode of diimines. The adduct with 2,2′-bipyrimidine (bpm) is dimeric with a μ-κ2N,N′:κ2N,N′-bridging coordination mode of bpm, while with 4,7-dimethyl-1,10-phenanthroline (phenMe2) a dimer is formed due to Te-(η6-C6) contacts. Te⋯N and Te⋯C interactions between Te(Cat36)2 and the diimines were found to be attractive and non-covalent (DFT and QTAIM). In accordance with the weakness of Te⋯N interactions, no ligand-to-ligand charge transfer (LLCT) bands were observed in the electronic spectra of the adducts. [ABSTRACT FROM AUTHOR]

α-Functionalisation of cyclic imines is explored. The cyclic imine substrates are synthesised from their respective halonitrile precursors using a nucleophilic addition/cyclisation sequence. Selective monohalogenation of the cyclic imines yields α-haloimines, which serve as a platform to obtain various α-hydroxyimine derivatives. In addition, an unusual tautomerisation and oxidation sequence is observed in the attempted preparation of α-hydroxyimines. [ABSTRACT FROM AUTHOR]

A convenient cyano source for the nucleophilic 1,4‐addition to enones and 1,2‐addition to imines has been developed, by generating the cyano unit in situ. via the TCT‐assisted dehydration of formamide. This protocol distinguishes itself by transition‐metal/ligand free conditions, compatibility with 1,4‐/1,2‐addition, readily available substrates and versatile synthetic utilities of the cyanated products. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Although it offers a direct route to access synthetically valuable α‐chiral primary amines, asymmetric transfer hydrogenation of NH imines has been rarely studied, due in large part to the inaccessibility and instability of NH imines. Herein, we report a Rh‐catalyzed asymmetric transfer hydrogenation of a kind of novel and stable NH imines which are prepared via condensation of easily available sulfonylated 2'‐aminoacetophenones with NH3 in methanol. With this method, enantioenriched chiral 2‐(1‐aminoalkyl)anilines, which are privileged pharmacore groups, have been synthesized with good functional group compatibility, and with up to 99% ee. A gram‐scale reaction using 0.2 mol% of catalyst has been successfully performed to highlight the practicality. Furthermore, the products can be derivatized into enantiopure bioactive molecules as well as chiral tridentate ligands for metal catalysis. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Herein, we report rhodium catalyzed N‐arylation via addition of arylboronic acids to electron‐deficient α‐iminoesters which can be prepared in high efficiency by using easily accessible β‐carbonyl esters. The reaction is highly regiospecific to achieve the N‐aryl addition efficiently with up to 99% yield under mild conditions. The corresponding product can be further efficiently converted into indoles and a series of other important building blocks. [ABSTRACT FROM AUTHOR]

The reactions of 3-aminopyridine with 9,10-phenanthrenequinone and 1,2-naphthoquinone under various conditions was studied. The formation of the monoimine was observed in the presence of an additional aromatic ring in the structure of the starting dione. The product of the nucleophilic attack of the amino group at position C4 of the aromatic ring was obtained in the absence of this additional ring. One of the products obtained is a derivative of lawsone, a natural dye with a wide range of bioactivity, including antitumor one. Its structure was additionally confirmed by single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The article discusses the polymerization scheme of benzoxazine monomer based on 4,4′‐diaminodiphenylmethane (P‐ddm) and the chemical structure of polybenzoxazine based on it poly(P‐ddm). The polymerization behavior of benzoxazine P‐ddm is studied using differential scanning calorimetry (DSC). Solid‐state 13C MAS NMR is used to determine the chemical structure of poly(P‐ddm). It is revealed that the сhemical structure of poly(P‐ddm) predominantly consists not of phenolic Mannich bridges, as expected, but of methylene bridges, which indicates the process of deamination of phenolic Mannich bridges. However, no weight loss associated with the expected release of free amine during this process is detected. This may indicate the incorporation of a diamine moiety into the polymer chain through the formation of imine bonds, the signal of which is detected in the 13C MAS NMR and FTIR spectra of the poly(P‐ddm), and on the 1H and 13C NMR spectra of model polybenzoxazine based on p‐cresol and 4,4′‐diaminodiphenylmethane poly(pC‐ddm). Based on the data obtained, a hypothesis is put forward about the formation of a network polymer, the structure of which consists mainly of methylene and imine units. [ABSTRACT FROM AUTHOR]

The photocatalytic oxidation and generation/regeneration of amines to imines and leucodopaminechrome (LDC)/NADH are subjects of intense interest in contemporary research. Imines serve as crucial intermediates for the synthesis of solar fuels, fine chemicals, agricultural chemicals, and pharmaceuticals. While significant progress has been made in developing efficient processes for the oxidation and generation/regeneration of secondary amines, the oxidation of primary amines has received comparatively less attention until recently. This discrepancy can be attributed to the high reactivity of imines generated from primary amines, which are prone to dehydrogenation into nitriles. In this study, we present the synthesis and characterization of a novel polymer‐based photocatalyst, denoted as PMMA‐DNH, designed for solar light‐harvesting applications. PMMA‐DNH incorporates the light‐harvesting molecule dinitrophenyl hydrazine (DNH) at varying concentrations (5%, 10%, 20%, 30%, and 40%). Leveraging its high molar extinction coefficient and slow charge recombination, the 30% DNH‐incorporated PMMA photocatalyst proves to be particularly efficient. This photocatalytic system demonstrates exceptional yields (96.5%) in imine production and high generation/regeneration rates for LDC/NADH (65.27%/78.77%). The research presented herein emphasizes the development and application of a newly engineered polymer‐based photocatalyst, which holds significant promise for direct solar‐assisted chemical synthesis in diverse commercial applications. [ABSTRACT FROM AUTHOR]

Some aryl E-imines were synthesized by nano-fly-ash H3PO4-catalyzed condensation of various aryl anilines and benzaldehydes under ultrasound irradiated greener solvent medium. In this condensation, the obtained yield was more than 75%. These E-imines were characterized by their physico-chemical data, microanalysis, and spectroscopic data. The characteristic spectral frequencies were employed for spectral quantitative structure–activity relationship study. The spectral QSAR study was performed with single and multi-regression analysis using Hammett σ, σ, σI, σRFR, and Swain–Lupton's constants. From the outcome of the regression, the effect of substituents on the spectral frequencies was predicted. The molecular docking study of these imines was performed by the assessment of protein–ligand interaction study with a characteristic protein. The antimicrobial activities of these imines were studied using the Bauer–Kirby disk diffusion technique with various bacterial and fungal microbes. The in vitro antimalarial activity of these imines was measured using P. Falciparum Thai protein microbes. [ABSTRACT FROM AUTHOR]

Sodium borohydride induces the oxidative expansion of the imine derived from isatin and phenylethylamine to form 3-phenethylquinazoline-2,4(1H,3H)-dione. It has been proposed that this transformation occurs by in situ formation of hydroperoxyl anions by a reaction between sodium borohydride and atmospheric oxygen. To contribute to understanding this oxidative expansion, the reaction between the imine derived from isatin and phenylethylamine with hydrogen peroxide was studied in this work. From this reaction, 3-phenethylquinazoline-2,4(1H,3H)-dione was isolated and two by-products were identified: N-phenethyl-2-(3-phenethyl-ureido)-benzamide and methyl(2-(phenethylcarbamoyl)phenyl)carbamate. This article analyses the structure of these by-products and proposes a mechanism that explains the reaction. It was established that the reaction of the imine derived from isatin and phenylethylamine with hydrogen peroxide produces a mixture of three compounds: 3-phenethylquinazoline-2,4(1H,3H)-dione, N-phenethyl-2-(3-phenethyl-ureido)-benzamide and methyl(2-(phenethylcarbamoyl)phenyl)carbamate. A reaction mechanism is proposed that explains this behaviour [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with a donor‐acceptor (D−A) architecture have been investigated as prospective semiconducting materials, particularly for photocatalytic processes. The incorporation of electron donating and accepting moieties into the COF backbone creates nano heterojunctions, enhancing efficient light absorption, charge separation, and charge transport. Herein, three pyrene‐based COFs were well designed for the aerobic coupling of amines under air atmosphere with blue‐LED irradiation. Among the three COFs, the Py‐Por‐COF with D−A structure exhibits the highest photocatalytic performance and demonstrates a remarkable apparent quantum efficiency of 11.3 % at 420 nm. In addition, the Py‐Por‐COF maintains a good level of crystallinity and high yield even undergone four cycles, showcasing the exceptional potential of D−A structure COFs in the field of photocatalytic organic transformation. [ABSTRACT FROM AUTHOR]

A formal [4+3] cycloaddition of 2‐alkylidenetrimethylene carbonates with quinazoline‐derived azomethine imines is described. Under Pd catalysis, the reaction works efficiently under room temperature to afford angular quinazoline‐fused seven‐membered N,N,O‐heterocycles. A variety of cyclic carbonates and azomethine imines were well tolerated under mild reaction conditions. This work demonstrates the synthetic utility of decarboxylative cycloadditions of 2‐alkylidenetrimethylene carbonates for the synthesis of angular polycyclic aromatic molecules. [ABSTRACT FROM AUTHOR]

We report the addition reaction of lithium enol ethers to fluoroalkyl imines. A range of different fluoroalkyls and lithiated reagents are well tolerated. Diastereoselective addition of lithium vinyl ethers to fluoroalkyl N‐tert‐butylsulfinylimines is disclosed, providing enantiomerically enriched α‐fluorinated amines in up to 98% yield. This general approach led to the diastereoselective formation of various amino alcohols and amino ethers, which are difficult to obtain by other methods. [ABSTRACT FROM AUTHOR]